It is a known technique to determine whether a captured foreign object, which is captured between an openable and closable member (e.g., a window glass) installed in a door of a vehicle and a corresponding neighboring member of the door located in the vicinity of the openable and closable member, is present. In this type of openable and closable member control apparatus, normally, when it is determined that the captured foreign object is present, the opening or closing operation of the openable and closable member is interrupted, and an operation, which is opposite to the interrupted operation, is executed to release the captured foreign object. With respect to the above control operation, for example, it is known that a threshold value is set for a measurement value (e.g., a rotational speed of the motor that is rotated to open or close the window glass), which varies according to a load applied to the window glass. The threshold value and the measured value are compared with each other to determine whether the captured foreign object is present.
When an operation (e.g., a switch operation) for starting the movement of the openable and closable member is performed, the drive source (the motor) is driven upon receiving a corresponding operational command. However, this type of drive source cannot be stably rotated at the start time of the drive source.
Thus, in order to correctly sense the capturing of the foreign object, an initial mask period, during which sensing of the clamping or drawing of the foreign object is not performed, is set until the rotation of the drive source is stabilized (see, for example, JP2006-322232A that corresponds to US2006/0119301A1).
As one example of this technique, in JP2006-322232A (corresponds to US2006/0119301A1), a time period from a time point of starting rotation of the motor (serving as the drive source) to a time point of reaching a stable rotational speed of the motor, is set as an activation/cancellation time period (initial mask period).
In this technique, the activation/cancellation time period is set in view of a peak of a change in the rotational speed of the motor since the time point of starting the rotation of the motor.
That is, when the peak is sensed, a decrease rate of the rotational speed of the motor is continuously measured. Furthermore, a time period Ta, which is from the time point of starting the rotation of the motor to a time point of reaching a maximum decrease rate of the rotational speed of the motor, is measured. A time period Tb, which is obtained by multiplying a vibration period of the door by a predetermined number, is added to the time period Ta, so that the activation/cancellation time period (the initial mask period) is set.
According to this technique, the appropriate cancel time period (the mask period) can be set even in a case where the assembling accuracy of the window glass is in the low level, and thereby the window glass is wobbled in multiple directions to generate a clearance between the window glass and a drive system thereof, resulting in high speed rotation of the motor in a state that is close to a no-load state of the motor, thereby causing generation of multiple peaks in the rotational speed of the motor.
However, in the above prior art technique, the slide resistance between the window glass and a weather strip is increased. Thereby, the above prior art technique cannot be used in a case where the operational load of the drive source becomes large.
This state (i.e., the state, in which the operational load of the drive source is large) occurs, for instance, at the time when the temperature the surrounding environment is low. However, the prior art technique cannot sense occurrence of this state and cannot correct the operation to set an appropriate mask period.
Thus, it has been demanded to develop a technique that can limit occurrence of erroneous reverse rotation and erroneous stop of the drive source (the motor) while maintaining a safety of an occupant of the vehicle by setting an appropriate mask period even in the state where the drive source is operated with the high load.